Capless multiaxial screw and spinal fixation assembly and method

ABSTRACT

A spinal fixation assembly and capless multi-axial screw system and method are shown. The assembly comprises a receiver having a rotary lock which in one embodiment includes a plurality of channels which urge and lock the elongated member to the screw using a bayonet type connection.

BACKGROUND OF THE INVENTION

This invention relates to a capless multiaxial screw and spinal fixationassembly and method, particularly useful for fixing and/or aligningvertebrae of the spine. The invention permits multiple angularorientations of an elongated member or rod with respect to a screw thatis screwed into a vertebra.

Various methods of spinal immobilization have been known and used in thepast. The preferred treatment for spinal stabilization is immobilizationof the joint by surgical fusion or anthrodesis. This method has beenknown since development in 1911 by Hibbs and Albe. However, in manycases, in particular cases involving fusion across the lumbosacralarticulation and where there are many levels involved, pseudorarthrosisis a problem. It was discovered that immediate immobilization wasnecessary in order to allow a bony union to form. Post operativeexternal immobilization, such as the use of splints and casts, was afavored method of treatment, however, as surgical techniques have becomemore sophisticated, various methods of internal and external fixationhave been developed.

Internal fixation refers to therapeutic methods of stabilization whichare wholly internal to the patient and include commonly known devicessuch as bone plates and pins. External fixation, in contrast, involvesat least some portion of stabilization device which is external to thepatient's body. Internal fixation is now the favored method ofimmobilization because the patient is allowed greater freedom with theelimination of the external portion of the device and the possibility ofinfection, such as a pin tract infection is reduced.

There have been numerous systems and methods developed in the past forcorrecting and stabilizing and aligning the spine for facilitating, forexample, fusion at various levels or areas of the spine, such as thosedevices are shown in U.S. Pat. Nos. 4,085,744; 4,269,178; 4,805,602;5,466,237; 5,474,555; 5,891,145; and 6,869,433 B2. Bone screws with apolyaxial head are commonly used in spine surgery today. They are usedchiefly in the lumbar spine and screwed into bone (pedicle) posteriorly.The head of the screw is attached to the shaft of the screw by means ofa ball and socket. The top of the screw is machined into a ball, and thehead contains a socket into which the ball fits. The screw head furthercontains a receiver for receiving a separate rod. The rod is fastened tothe screw head receiver via a threaded cap. The rod is then fastened toscrews placed in adjacent vertebrae thus providing stabilization. Thepolyaxial head allows the rod to be placed in a variety of angles withrespect to the screw allowing conformance to local anatomy.

When the threaded cap is tightened upon the rod, a frictional pressureis transmitted from the threaded cap to the rod thence to the top of theball, thus locking the ball-in-socket and preventing motion aftertightening has occurred. This concept is demonstrated in U.S. Pat. Nos.5,466,237 and 5,474,555, which illustrate this type of screw.

U.S. Pat. No. 5,466,237 to Bird et al. discloses a bone screw having aspherical projection on the top of the bone screw. An externallythreaded receiver member supports the bone screw and spinal rod on topof the spherical projection. An outer nut is tightened onto the receivermember to press the spinal rod against the spherical projection toaccommodate various angular orientations of the bone screw relative tothe rod.

In another approach shown in U.S. Pat. No. 4,946,458 to Harms, aspherical headed bone screw supported within separate halves of areceiving member. The bottom of the halves are held together by aretaining ring. The top of the receiver halves are compressed about thebone screw by nuts threaded onto a threaded spinal rod.

In still another approach taken by Harms et al. in U.S. Pat. No.5,207,678, a receiver member is flexibly connected about a partiallyspherical head of a bone screw. Conical nuts on opposite sides of thereceiver member threaded onto a threaded rod passing through thereceiver. As the conical nuts are threaded toward each other, thereceiver member flexibly compresses around the head of the bone screw toclamp the bone screw in its variable angular position. One detriment ofthe systems in the two Harms et al. patents is that the spinal rod mustbe threaded in order to accept the compression nuts.

U.S. Pat. No. 6,869,433 discloses the use of a pedicle screw assemblythat comprises a screw having a head with a convex portion and areceiver that receives the head. The receiver also receives an elongatedmember, such as a spinal fixation rod. The receiver has a concaveportion which has a radius of curvature which is less than the radius ofcurvature of the convex portion of the head whereby to create aninterference fit between the convex portion of the head and the concaveportion of the receiver. The device also includes an internal nut andexternal nut that compresses the rod against a pressure disc which inturn compresses the head convex portion of the screw into the receiverconcave portion and locks the angular position of the receiver withrespect to the screw.

One of the problems with the prior art devices is the number of partsand components, especially those components that utilize a threaded capscrew to secure the rod to the anchoring screw, whether internal orexternal, to fix the rod relative to the screw. Problems with thethreaded fastener, that is, threaded cap or set screw, are numerous andinclude risk of cap loosening, loss of cap intra-operatively, crossthreading, thread failure, failure of the cap in driving instrument andlimitations upon torque application.

What is needed, therefore, is a system and method that provide a lock orconnection between the rod and screw without the use of external nuts,screws, caps or threads of the type shown in the prior art.

These and other objects and advantages of the invention will be apparentfrom the following description, the accompanying drawing and theappended claims.

SUMMARY OF THE INVENTION

The present invention improves the spinal fixation and the lockingbetween an elongated member or rod and a screw.

One object of the invention is to provide a system and method thatreduces or eliminates the need for external or internal caps or screwsto lock the relative position of a rod to a screw.

Another object of the invention is to provide a simple bayonet-typeconnection that eliminates the fixation systems of the past and/orsimplifies the spinal fixation procedure.

In one aspect, this invention discloses a capless multiaxial screwcomprising a screw having a threaded portion and a screw head, areceiver having a bore for receiving the threaded portion and areceiving channel for receiving an elongated member, the channel furthercomprising a locking channel in communication with the channel, acompression member for situating in the bore, the compression membercomprising a second receiving channel having a first end and a secondend and further associated with a first end, and a receiving areaassociated with the second end for receiving and engaging the screwhead, the elongated member cooperating with the compression member tolock the elongated member to the screw when the elongated member isreceived in the first and second receiving channels and the receiver isrotated from an unlocked position to a locked position.

In another aspect, this invention discloses a spinal fixation assemblycomprising a receiver having a bore for receiving a screw having a screwhead that is larger than a diameter of the bore, and a compressionmember dimensioned to be received in the bore and having a first end forreceiving an elongated member and a second end for engaging the screwhead, the receiver comprising a receiving channel for receiving theelongated member and a locking channel for locking the elongated memberto the screw when the receiver is rotated from an unlocked to a lockedposition.

In yet another aspect, this invention relates to a spinal fixationassembly comprising a receiver having a bore for receiving a screwhaving a screw head that is larger than a diameter of the bore and areceiving channel for receiving an elongated member, and a compressionmember dimensioned to be received in the bore and having a first end forengaging the elongated member and a second end for engaging the screwhead, the receiver comprising a rotary lock for locking the elongatedmember to the screw.

In still another aspect, this invention relates to a spinal fixationassembly comprising a receiver having a bore for receiving a screwhaving a screw head, and a compression member dimensioned to be receivedin the bore and having a first end for engagement with an elongatedmember and a second end for engagement with the screw head, the receivercomprising a locking channel and a receiving channel coupling thelocking channels, the receiving channel receiving the elongated memberand the locking channels cooperating to secure the elongated member tothe screw when the receiver is rotated.

In another aspect, this invention discloses a spinal fixation assemblycomprising a receiver having a bore for receiving a screw having a screwhead, and a compression member dimensioned to be received in the boreand having a first end and a second end, the receiver comprising anintegral rotary lock for locking the elongated member to the screw whenthe receiver is rotated.

In another aspect, this invention relates to a method for securing anelongated member to a spinal column, comprising the steps of screwing ascrew into a spinal bone, the screw having a head that is received in aseat of a receiver having a bore through which threads of the screw maypass, situating the rod into the receiver, and rotating the receiver tofasten the rod onto the screw.

These and other objects and advantages of the invention will be apparentfrom the following description, the accompanying drawing and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary perspective view of a capless multiaxial screwand fixation assembly mounted on a spinal column having a plurality ofvertebrae;

FIG. 2 is a perspective view of the system shown in FIG. 1;

FIG. 3 is an exploded fragmentary perspective view of the system shownin FIGS. 1 and 2;

FIG. 4 is a fragmentary perspective view illustrating a rod received ina receiving channel of a receiver;

FIG. 5 is a fragmentary plan view of the illustration shown in FIG. 4;

FIG. 6 is a fragmentary view similar to FIG. 4, but showing the receiverrotated approximately 30 degrees about its axis relative to the rod;

FIG. 7 is a fragmentary plan view similar to FIG. 5 and showing thereceiver in the position illustrated in FIG. 6;

FIG. 8 is fragmentary perspective view showing the receiver in a fullylocked position;

FIG. 9 is a plan view similar to FIGS. 5 and 7 showing the receiver in afully locked position;

FIG. 10 is a view taken along the line 10-10 in FIG. 4;

FIG. 11 is a view illustrating the rod after it has been received in thechannel of the receiver and supported above a bottom surface of acompression member;

FIG. 12 is a sectional view taken along the line 12-12 in FIG. 8;

FIG. 13 is a fragmentary view showing the rod in cross-section and in afully locked position;

FIG. 14 is a fragmentary view illustrating various features of thelocking channels;

FIG. 15 is a plan view showing a compression member received in a boreof the receiver and illustrating the aperture through which a tool maybe inserted to rotate the screw head before the rod is positioned in achannel of both the receiver and the compression member;

FIG. 16A-16E are various views of the receiver in accordance with oneillustration of the invention;

FIG. 17 is a sectional view of a compression member in accordance withone illustration of the invention;

FIG. 18 is a fragmentary sectional view of another illustration of theinvention, showing a channel having walls that are generally non-planarto define an intermediate area for loosely capturing the rod;

FIG. 19 is a side elevation view of the embodiment shown in FIG. 18;

FIG. 20 is a fragmentary sectional view that has been rotated relativeto FIGS. 18 and 19;

FIG. 21 is an elevational view rotated relative to FIG. 19;

FIGS. 22-24 are plan views illustrating rotational movement of thereceiver relative to the rod;

FIGS. 25-27 are side elevation views that generally correspond to FIGS.22-24, respectively, illustrating the receiver in various positions, butwith the rod removed for ease of illustration and understanding;

FIGS. 28-30 are views similar to FIGS. 25-27, respectively, illustratingthe receiver in various rotational positions relative to the rod as therod is moved from a receiving position to a locked position;

FIGS. 31-33 are fragmentary sectional views somewhat enlarged anddiagrammatic to simply illustrate the intermediate capturing step ofreceiving area for loosely capturing the rod in the receiver; and

FIG. 34 is a diagrammatic view which is presented for purposes ofillustrating various dimensions of the channels in the receiver or thesecond illustrative embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1-3, a capless multi-axial screw and spinalfixation assembly 10 and method are shown. The assembly 10 comprises ascrew 12 having a threaded portion 12 a and a head 12 b that in theembodiment being described, has a rounded profile or curvature, as bestillustrated in FIGS. 3 and 10-13. The screw head 12 b comprises a hexfemale opening 12 c for receiving a tool (not shown) for screwing thescrew 12 into an aperture 14 a of a spinal bone 14, such as a vertebraof a spine.

As illustrated in FIGS. 1 and 2, one feature of the invention is that itenables a user to fix a relative position of a plurality of vertebrae,such as vertebrae 14, 16 and 18 in FIG. 1, in a fixed and stabilizedposition.

The system 10 comprises a retainer or receiver 20 having a generallycylindrical receiver wall 20 c (FIG. 4) that defines an aperture or bore22 that traverses or extends along a receiver axis A (FIG. 11) theentire length of the receiver 20, as best illustrated in FIGS. 4, 10,and 12. The receiver 20 comprises a first end 20 a and a second end 20b, and although not shown, may comprise a chamfer 21 of about 45degrees. It should be understood that the internal wall 20 c defines aseat 20 d toward the bottom of the receiver 20 (as viewed in FIGS. 10and 15) that is arcuate or curved in cross section. The seat 20 d has aradius or curved surface R1 (FIG. 10). Note that a diameter or distanceD1 (FIG. 10) of bore 22 at the end 20 b of the receiver or retainer 20is slightly smaller than both a diameter or distance D2 (FIGS. 7 and 10)of the bore 22 at end 20 a and a diameter D3 (FIG. 12) of the roundedscrew head 12 b so that it defines the receiver seat 20 d (FIGS. 10 and15) for receiving or capturing the screw head 12 b. In this regard, thescrew head 12 b has an end 12 b 1 that is configured and dimensioned tobe received or captured in the seat 20 d and that can be rotated orscrewed while in the bore 22 (FIGS. 10 and 15). The end 12 b 2 has acurved or arcuate shape that generally complements the shape of the seat20 d to permit polyaxial and relative movement between the receiver 20and screw 12.

As shown in FIGS. 3 and 11-13, the bore 22 receives the threaded portion12 a of the screw 12 until the head 12 b is received in the seat 20 d(as illustrated in FIGS. 10-13). It should be understood that the seat20 d cooperates with the end 12 b 1 of head 12 b and permits theretainer or receiver 20 to move polyaxially about a center of head 12 bso that position of the receiver 20 may be altered relative to the head12 b of screw 12. This allows a user, such as a surgeon or physician, tochange the polyaxial position of the receiver 20 relative to the screw12 in order to adjust an angular position of an elongated member or rod24 relative to, for example, the vertebrae 14, 16 and 18 illustrated inFIG. 1. The rod 24 may be any suitable shape in cross section, such ascircular, hexagonal, octagonal, polygonal or the like.

Note that the receiver 20 comprises a receiving channel or slot 26 (FIG.15) defined by wall surfaces 21 a, 21 b, 21 c and 21 d (FIG. 4). Thereceiver 20 further comprises a lock, locking means, locking channel, orrotary lock 28 (FIGS. 11 and 12) which is integral with the receiver 20.In the embodiment being described, the receiver 20 is manufactured oftitanium and is machined to provide the receiving channel 26, lock 28and the bore 22 using conventional machining techniques. Other potentialmaterials include biocompatible load bearing material, such as metals,metal alloys, carbon fibers, composites, plastics or hybrid materials.

In one embodiment, the lock 28 cooperates and is in communication withthe receiving channel 26 to provide a continuous channel 30 forreceiving the elongated member or rod 24. The lock 28 cooperates withthe receiving channel 26 and urges rod 24 toward the screw head 12 b andvertebra, such as one of the vertebra 14-18 in FIG. 1, when the receiver20 is rotated in a clockwise direction (as viewed in FIG. 3). Thecontinuous channel 30 comprises a first channel 32, the channel 26, andthe second channel 34. The lock 28 and continuous channel 30 provides abayonet-type connection for coupling or fixing the receiver 20, the rod24 and screw 12 together in the manner described herein.

Note that the lock 28 comprises the first channel 32 and a secondchannel 34 (FIGS. 12 and 13) that extend or spiral, as illustrated inFIGS. 16A-16E, about the receiver axis A (FIG. 11) of receiver 20. Thefirst and second channels 32 and 34 generally spiral or revolve from thefirst end 20 a of receiver 20 toward the second end 20 b, as shown inFIGS. 10-13 and 16A-16D. Thus, in the embodiment being described, thefirst and second channels 32 and 34 are non-linear and spiral or revolvein a general helix about the axis A of the receiver 20. In theillustration, the channels 32 and 34 spiral or revolve in the samedirection about the axis A, as shown in FIGS. 16A-16D. Note that thechannels 32 and 34 are in communication with both the receiver bore 22and receiving channel 26 of receiver 20. During operation, the channels32 (FIG. 11) and 34 (FIG. 12) receive the rod 24 after it has beenreceived in channel 26 and urge or force the rod 24 toward the screwhead 12 b and vertebra, such as vertebra 14 in FIG. 1, when the receiver20 is rotated in a clockwise direction in the illustration beingdescribed.

As illustrated in FIGS. 11 and 16A, the first channel 32 is defined by afirst surface or wall 20 e, a generally opposing second surface or wall20 g, and a third surface wall 20 f that joins the walls 20 e and 20 gin the receiver 20. A fourth surface or wall 20 h, a generally opposingfifth wall 20 i, and a sixth surface or wall 20 j that joins walls 20 hand 20 i cooperate to define the second channel 34 (FIGS. 12 and 16D).Note that the walls 20 e and 20 g are generally parallel and walls 20 hand 20 i are generally parallel. In the illustration being described,the walls 20 e and 20 g and 20 h and 20 i are generally planar and havegenerally constant distance D4 (FIG. 13) and D5 (FIGS. 11 and 12)therebetween. However, in the illustration described later hereinrelative to FIGS. 18-32, the opposing walls 20 e, 20 g, 20 h and 20 imay be non-planar so that the distance or dimensions D9 and D10 varyalong the length of the channels 32 and 34.

The channels 32 and 34 generally lay in planes P1 and P2 that are at theangles C (FIG. 14) and D, respectively, relative to the axis A of thereceiver 20. As described later herein, the walls 20 e and 20 h engageand cam against the rod 24 and force or urge it downward (as viewed inFIGS. 10-15) in response to the rotary movement of the receiver 20. Inanother embodiment described later herein, the walls 20 e and 20 g andwalls 20 h and 20 i may comprise a curved or arcuate area and maycooperate to define an intermediate rod capturing area, as describedbelow relative to FIGS. 18-34.

As illustrated in FIGS. 4 and 11, note that the channel 32 is defined bythe walls 20 e, 20 f, 20 g and generally curved or arcuate wall portion50 that couples wall 20 g to surface 21 b (FIGS. 4 and 16A) of channel26. The generally curved arcuate wall portion 50 also generally definesan intersection or transition from the receiving channel 26 to the firstlocking channel 32 of lock 28. The channel 34 is defined by 20 h, 20 iand 20 j and a third generally curved or arcuate wall 52 that joins thewall 20 i to walls 21 d (FIGS. 4 and 16C). The wall 52 provides anintersection or transition between channel 26 and the second lockingchannel 34. Notice that the wall portions 20 f (FIG. 11) and 20 j (FIG.12) also each have a radius of curvature that generally complements theradius of curvature or circumference of the rod 24 so that when the rod24 is moved from the unlocked position (illustrated in FIGS. 4, 5, 10and 11) to a locked position (illustrated in FIGS. 8, 9, 12 and 13), therod 24 is received and positioned against the wall portions 20 f and 20j as shown.

The system 10 may further comprise a compression member 40 (FIGS. 3 and17). The compression member 40 comprises a wall 40 a that defines asecond generally U-shaped receiving channel 42. The compression member40 also comprises a frusto-conical seat or concave area 41 (FIGS. 10 and17), defined by a tapered wall or surface 40 b, that engages the roundedshape of the end 12 b 1 (FIG. 3) of screw head 12 b. Although not shown,the system 10 could be provided without the compression member 40, sothat the rod 24 would engage the screw head 12 b directly, for example,when the receiver 20 is rotated as described later herein.

The compression member 40 comprises a length D6 (FIGS. 3 and 17) and adiameter D7 (FIG. 17) dimensioned to be received in the bore 22 asshown. The channel 42 defined by wall 40 a comprises a bottom surface 40c. The channel 42 is generally U-shaped in cross section and has a widthor dimension D8 (FIGS. 3, 7 and 17) and surface 40 c comprises a radiusof curvature R5 (FIG. 17) that generally complements or is slightlylarger than the circumference D9 (FIG. 3) of the rod 24.

During operation, the compression member 40 is urged downward (as shownin FIGS. 10-13) in response to the rotary movement of the receiver 20.The rod 24 engages the bottom surface 40 c (FIGS. 12 and 17) of channel42 of compression member 40. This in turn causes surface 40 b to engageand apply a compressive force against the end 12 b 1 of screw head 12 bas the rod 24 is driven in the downward direction (as viewed in FIGS.10-13) and into the second channel 42. This movement forces andcompresses the seat 20 d against the end 12 b 2 of screw head 12 b ofthe receiver 20, thereby locking the screw head 12 b to the rod 24 andfixing the relationship of the receiver 20 relative to the screw head 12b.

Note that the compression member 40 (FIG. 17) also comprises a bore oraperture 43 defined by wall 40 d. The bore 43 has a dimension ordiameter D10 (FIG. 17). A surgeon or physician may insert a tool, suchas a hex head screwdriver (not shown), through channel 26, through bore22 of receiver 20 and through the bore 43 and into the hex femaleopening 12 c (FIG. 15), for example, to tighten or loosen the screw 12.Thus, it should be understood, as illustrated in FIG. 15, that the hexfemale opening 12 c of screw 12 b is accessible after the screw 12 isinserted through the bone 22 and compression member 40 is situated inthe bore 22.

Referring back to FIGS. 10-16E, the receiving channel 26 (FIG. 11) ofreceiver 20 extends from an end 20 a of receiver 20 in an axialdirection and lies in a plane P3 (FIG. 15) that is generally planar andextends downward along the axis A (as viewed in FIG. 14). In contrast,the lock 28 defined by the locking channels 32 and 34 revolve, spiral orextend laterally or radially at distances that are generally constantrelative to axis A and that vary, such as increase, relative to end 20 aof receiver 20. As mentioned earlier, each of the channels 32 and 34spiral in a general helix downward from the receiving channel 26 andabout the axis A of the receiver 20 as shown in FIGS. 10-13 and 16A-16D.Note that the channels 32 and 34 lay in the planes P1 and P2 (FIG. 14),respectively, that intersect axis A at the predetermined anglesindicated by double arrows C and D. The predetermined angles C and D areacute angles in the embodiment being described.

As shown in FIGS. 16A and 16B, the channel 32 is inclined relative to aradial line of receiver 20 at a third angle (indicated by double arrow Ein FIG. 16A) relative to end 20 a. Channel 34 is also inclined relativeto a radial line at a fourth angle F (FIG. 16B). Although not shown, itis contemplated that other designs, configurations or arrangements ofchannels 32 and 34 and the lock 28 may be provided, such as channels(not shown) that extend about axis A, but that do not spiral and/or thatare not at the inclined angles E and F, such as channels that extend atdistances that are generally constant relative to end 20 a.

An operation or method regarding this illustration will now bedescribed. As illustrated in FIGS. 3-9 and 15, the screw 12, togetherwith receiver 20 are screwed into vertebra 14 during which a physicianor surgeon screws the threaded portion 12 b of screw 12 in the aperture14 a of the vertebra 14 using a tool (not shown), such as a hex wrenchor screwdriver (not shown), that is inserted through channel 26, bore 22and bore 43. In one embodiment, the receiver 20, screw 12 andcompression member 40 may be provided in a pre-assembled unit prior tosurgery, so no assembly is required by the physician. The screw 12 isscrewed substantially all the way into vertebrae 14, but is left withspace between the receiver 20 and vertebrae 14 so that an angular orpolyaxial position of the receiver 20 may be adjusted or changed duringthe operation.

The channel 26 of receiver 20 and channel 42 of compression member 40are provided or arranged in a common plane P3, as shown in FIGS. 4, 5and 15. The surgeon then places the rod 24 into the channels 26 and 42and adjusts the multi-axial or polyaxial position of the receiver 20relative to the rod 24. As mentioned earlier, the channel 26 and bores22 (FIG. 10) and 43 (FIG. 17) provide a continuous opening or area 49through which the physician or surgeon may insert a tool, such as a hextool, to turn, rotate and/or tighten or loosen the screw 12 in thedesired direction prior to placing the rod 24 into channel 26. At thispoint, the rod 24 remains in an unlocked position.

Note that the rod 24 is supported by and between the arcuate or roundedwall portions 50 and 52, which causes the rod 24 to be situated abovethe bottom surface 40 c of the channel 42 of compression member 40, asillustrated in FIGS. 10 and 11. Note that the arcuate or curved wallportions 50 and 52 each comprise a radius of curvatures R2 (FIGS. 11, 14and 16 a) and R3 (FIGS. 13 and 14), respectively, that generallycomplements or is larger than a radius of curvature or circumference ofthe rod 24, as illustrated in FIGS. 11 and 13.

The camming or bayonet type action of the rotary lock 28 on receiver 20forces the rod 24 in an axial direction parallel with axis A of receiver20 when the receiver 20 is turned or rotated with a tool, such as ascrewdriver (not shown), placed in channel 26, as illustrated in FIGS. 6and 7. This rotary movement or action forces the rod 24 downward (asviewed in FIG. 10) and into the channels 32 and 34. As the receiver 20is rotated further, as shown in FIGS. 8 and 9, the walls 20 e and 20 g(FIG. 11) of channel 32 and walls 20 h and 20 i (FIG. 12) of channel 34act upon, force or urge the rod 24 downward (as viewed in FIGS. 10-13)and into the second channel 42 of compression member 40 until it engagesthe surface 40 c of compression member 40. As the receiver 20 is rotatedfurther, the rod 24 urges the compression member 40 toward the screwhead 12 b 1 and forces wall 40 b of the compression member 40 againstthe screw head 12 b of screw 12 with a compressive force which causesthe screw head 12 b to become fastened or locked to the rod 24, therebyfixing the receiver 20 and rod 24 to the screw 12.

It should be appreciated that when the rod 24 is in the locked positionshown in FIGS. 8, 9, 12 and 13, the rod 24 engages surfaces 20 e, 20 f,and 20 g of channel 32 and surfaces 20 h, 20 i and 20 j of channel 34and surface 40 c of second channel 42. The seat 40 d of compressionmember 40 engages screw head 12 b 2. These surfaces cooperate to retainrod 24 in the locked position. The surfaces 20 f and 20 j comprise aradius of curvature R4 of about φ0.100-φ0.130 inch. A raised detentportion or bump 59 (which is only shown in FIG. 13 for ease ofillustration) may be provided in each channel 32 and 34, as shown inFIG. 13 relative to channel 32. The detent 59 is provided to facilitateretaining the rod 24 in the locked position.

Thus, as illustrated in FIGS. 1, 2 and 4-9, a surgeon may use one or aplurality of spinal fixation assemblies 10 during a spinal fixationprocedure. For example, the surgeon may use a plurality receivers 20 andscrews 12 with one rod 24, as illustrated in FIGS. 1 and 2. In theillustration, the surgeon screws the screws 12 into a plurality ofvertebrae, such as vertebrae 14, 16 and 18 illustrated in FIG. 1, andgenerally aligns the channels 26 of receivers 20. The surgeon theninserts the tool, such as a hex tool (not shown), through bores 22 and43 and into female slot 12 c in screw head 12 and screws the screw 12until the bottom 20 b of the receiver 20 engages or is proximatelylocated against its respective vertebra.

If the compression member 40 is being used, compression member 40 islocated in each bore 22 of each receiver 20 and generally aligns thechannels 42 and 26, as illustrated in FIGS. 4, 10 and 15. It should beunderstood that when the spinal fixation assembly 10 is in the unlockedposition, the channels 26 and 42 are generally parallel or lie in thecommon plane P3 as shown in FIG. 15. The rod 24 is then placed inchannel 26, whereupon it becomes supported by walls 50 and 52 (FIG. 4)and by wall portions 50 and 52 (FIGS. 4 and 11). This causes rod 24 tobe supported slightly above the bottom 40 c of channel 42 of receiver40, as mentioned earlier and as illustrated in FIGS. 10 and 11.

At this point in the procedure, the surgeon aligns the rod 24 in thereceiver 20 to the desired position relative to the spine, vertebrae andother receivers 20 that are being used. He positions the rod 24 andpolyaxial or angular position of each receiver(s) 20 relative thereto.It should be understood that the screws and position of the vertebrae,such as vertebrae 14-18, relative to each other may also be adjusted.Once the bones 14-18 are adjusted and angular or polyaxial position ofeach receiver 20 is adjusted, the surgeon locks each receiver 20 to rod24 by rotating or turning the receiver 20 with a tool, such as ascrewdriver (not shown), placed in slot 26. This causes the receivers 20to become fixed or locked onto their respective screws 12 and the spinalbones 14-18 (FIG. 1) to become aligned and fixed into the desiredposition.

It should be understood that before the rod 24 is placed in thereceiving channel 26 and the receiver 20 is rotated, the surgeon maytighten one or more screws 12 to a tighter or fixed seated position bysituating the tool, such as a hex wrench (not shown), through theaperture 43 (FIG. 15) defined by the wall 40 d of the compression member40 and into the hexagonal female slot 12 c in the screw head 12 b. Afterthe screw 12 is tightened to the desired tightness or torque, thesurgeon places the rod 24 into the channels 26 and 42 (FIGS. 4, 5, 10and 11) of the one or more of the receivers 20 being used.

As mentioned, the surgeon rotates the receiver 20 about its axis, asillustrated in FIGS. 3, 6 and 7 using a tool, such as a screwdriver (notshown), in the clockwise direction, as illustrated in FIGS. 6 and 7.During this rotation of receiver 20, the compression member 40 and rod24 do not rotate. As alluded to earlier, walls 20 e and 20 g (FIG. 11)and walls 20 h and 20 i (FIG. 12) urge the rod 24 toward the bottom ofchannels 32 and 34 and urge the rod 24 to move downward (as viewed inFIGS. 10 and 12) toward the surface 40 c or bottom of the channel 42where it engages the surface 40 c, as illustrated in FIGS. 4-9 and10-13. The rod 24 is also supported by and compresses against thesurface 40 c of compression member 40. The seat 40 d is caused to engagethe screw head 12 b 2.

Thus, when it is desired to lock the receiver 20 and the screw 12 to therod 24, the surgeon rotates the receiver 20 in the clockwise direction,as illustrated in FIGS. 6 and 7, using the conventional tool, such as aregular screwdriver. The receiver 20 is rotated until it is moved fromthe unlocked to the locked position, as illustrated in FIGS. 8, 9, 12and 13. Note that in the locked position, the rod 24 is received andengages the walls 20 f and 20 j associated with the ends of channels 32and 34, respectively.

Thus, it should be understood that when receiver 20 is rotated, thewalls 20 e and 20 h provide the camming force necessary to cam and urgethe rod 24 against the receiver 40. This, in turn, causes the surface orwall 40 b of receiver 40 to compress and lock against the end portion 12b 2 (FIG. 3) of screw head 12 b. The wall 40 b of compression member 40cooperates with the curved seat defined by wall 20 d (FIG. 10) and trapsor locks the screw head 12 b to the rod 24.

As illustrated in FIGS. 8, 9, 12 and 13, notice that the channel 26 liesin an imaginary plane that is generally perpendicular to the imaginaryplane in which the channel 42 and an axis of rod 24 when the receiver 20is in the locked position.

It should be appreciated from the foregoing that the receiving channel26 is in communication with the channels 32 and 34 of lock 28 and thatthe lock 28 cooperates with the rod 24 to not only lock the rod 24 tothe screw 12, but also to fix a position of the vertebrae 14, 16 and 18.

When it is desired to unlock the rod 24 from the screw 12, the surgeonsimply rotates the receiver 20 in a counterclockwise direction in theillustration and reverses the procedure.

Referring now to FIGS. 18-34, another illustrative embodiment is shown.Those parts that are the same as the parts relative to FIGS. 1-17 havebeen labeled with the same part number, except that the part numbers inthe embodiment described in FIGS. 18-34 have a prime mark (“′”)associated therewith. The FIGS. 31-34 are diagrammatic enlargedsectional views for ease of illustration.

Note in the embodiment in FIGS. 18-34, the receiver 20′ compriseschannels 32′ and 34′ that each have a cross-sectional dimension thatvaries over the length of the channels 32′ and 34′ to provide anintermediate holding area 60 where the rod 24′ is loosely captured inthe channels 32′ and 34′. The channels 32′ and 34′ each have anintroducing area 60 a, an intermediate holding or receiving area 60 band a locking area 60 c. For ease of illustration and description, thereceiving area 60 b will be described relative to channel 32′; however,it should be understood that the channel 34′ in the second illustrationcomprises substantially the same configuration.

It should be appreciated that the intermediate area 60 b in the channels32′ and 34′ enable an intermediate step between initial rod 24′insertion and final rod 24′ locking. In other words, this is a rod 24′capturing step during which the rod 24′ is loosely captured in thereceiver 20′, but it is not rigidly locked into place against screw 12′yet. This allows the surgeon greater ease and flexibility when headjusts the screws 12′ position with respect to the rod 24′ while therod 24′ is in place. For example, the surgeon may move the screws 12′closer together (compression) or In the illustration being described,the intermediate capturing step is accomplished by rotating the receiver20′ partially, such as approximately 30 degrees in the illustration asshown in FIGS. 23, 26 and 29, which forces the rod 24′ from theintroducing area 60 a into the intermediate area 60 b.

The introduction area comprises an associated dimension D13 (FIG. 34)and the locking area 60 c has an associated dimension D14 (FIG. 34). Theintermediate area 60 b has an associated intermediate dimension D15(FIG. 34) between the wall 62 and wall 64 that is slightly larger thanthe diameter of the rod 24′ and the dimensions D13 and D14 associatedwith the introduction area 60 a and locking area 60 c, respectively. Itis dimensioned to accommodate the rod 24′ and to capture the rod 24′loosely so that the rod 24′ can easily slide between the walls 62 and 64and is not locked. This facilitates the surgeon adjusting a position ofthe screws 12′ in vertebrae, such as vertebrae 14′-18′, relative to aposition of the rod 24. Once the screws 12′ are adjusted to the desiredposition, the physician or surgeon may then lock the receiver 20′ ontothe screw 12′ by inserting a tool, such as a screwdriver (not shown),into the slot 26′ and rotate the receiver 20′ in the clockwise directionas illustrated in FIGS. 22-30.

In the illustration shown in FIGS. 31-34, the channel 32′ is defined bya wall 62, a generally opposing second wall 64 and a joining wall 63that joins walls 62 and 64 as shown. Note that unlike the embodimentdescribed relative to FIGS. 1-17, the channel wall 62 has a first wallportion 62 a, a second wall portion 62 b and an intermediate wallportion 62 c that couples the wall portions 62 a and 62 b as shown. Theopposing channel wall 64 comprises the first wall portion 64 a, a secondwall portion 64 b and an intermediate wall portion 64 c that couples thefirst and second wall portions 64 a and 64 b as shown. In this regard,note that an intersection 66 is defined between the wall portions 64 aand 64 c. A second intersection 68 is defined between the wall portion62 b and 62 c as shown. The intersections 66 and 68 generally define anentrance to the intermediate area 60. The intermediate wall portions 62c and 64 c cooperate to define the intermediate area 60 b which receivesthe rod 24′ and loosely captures the rod 24′ in the receiver 20′.

The channels 32′ and 34′ are configured such that they comprise ordefine the introduction area 60 a for receiving the rod 24′ in thereceiver 20′, as illustrated in FIGS. 22, 25 and 28. The first wallportion 64 a provides a ramp 64 a 1 for directing the rod 24′ into theintermediate area 60 b when the receiver 20′ is rotated about 20-40degrees as shown in FIGS. 23, 26 and 29. As shown in the illustration,the surfaces 62 and 64 are not generally planar and have areas, such asintermediate wall portions 62 c and 64 c that are curved or recessed tofacilitate defining the intermediate area 60 b.

During a surgical procedure, the surgeon may make the desiredadjustments of the rod 24′ relative to the screws 12′ and vertebrae14′-18′ while the rod 24′ is loosely captured in the intermediate area60 b. The surgeon then uses the tool, such as a screwdriver (not shown),to rotate the receiver 20′ to the locked position shown in FIGS. 24, 27and 29. Similar to the embodiment described earlier herein relative toFIGS. 1-17, the receiver 20′ urges or forces the rod 24′ from theintermediate area 60 b to the locking area 60 c. The rod 24′ becomessituated in the locking area 60 c, whereupon the rod 24′ becomes lockedtherein. Note that the distance or dimension D12 (FIG. 8) between thesecond wall portions 64 b and 62 b is substantially the same or may besmaller than the diameter of the rod 24′. As the receiver 20′ is rotatedin the clockwise direction in the illustration being described, the wall62 slightly deflects upward (as viewed in FIG. 31, for example) topermit the rod 24 to be captured and locked in the locking area 60 c.Note that a wall portions 62, 63 and 64 comprises various radii ofcurvature R5-R9 having the illustrative dimensions or ranges ofdimensions set forth in the Table I below. For example, the radius ofcurvature R8 generally corresponds to the cross sectional circumferenceof the rod 24′ so that the rod 24′ becomes captured in the locking area60 c. As in the prior illustration, the detent 59 (FIG. 33) may beprovided in channels 60 and 62 to further facilitate retaining the rod24′ in the locking area 60 c.

Advantageously, this system and method facilitates providing a lockingreceiver 20 that reduces or eliminates the need for threading,internally or externally.

Advantageously, the immediate areas 60 b of channels 32′ and 34′ of thesecond embodiment are dimensioned and configured to facilitate lockingthe rod 24′ onto the screws 12′ while permitting ease of adjustmentbetween the receiver 20′ and the rod 24′ when the rod 24′ and receiver20′ are situated in the intermediate area 60 b′, as illustrated in FIGS.23, 26 and 29.

In the embodiments being described, the rod 24, screw 12, receiver 20and compression member 40 are all made of titanium alloy. Othermaterials may be used such as metals, metal alloys, carbon fibers,composites, plastics or hybrid materials. Various illustrativedimensions or possible ranges of dimensions are listed in the followingTable I: Illustrative/Approximate Part Number/Label Dimensions/Ranges D1(FIG. 10) φ.302 inch D2 (FIG. 10) φ.350 inch D3 (FIG. 12) φ.890 inch D4(FIG. 13) φ.590 inch D5 (FIG. 11) φ.230 inch D6 (FIG. 3) φ.400 inch D7(FIG. 17) φ.348 inch D8 (FIG. 3) φ.240 inch D9 (FIGS. 3) φ.218 inch D10(FIG. 17) φ.200 inch D11 (FIG. 3) 10 mm-60 mm D12 (FIG. 8)  2 mm-10 mmD13 (FIG. 34) φ.225 inch D14 (FIG. 34) φ.220 inch D15 (FIG. 34) φ.210inch R1 (FIG. 10) φ.115 inch R2 (FIG. 14) φ.340 inch R3 (FIG. 14) φ.340inch R4 (FIG. 12)    φ.100-φ.130 inch R5 (FIG. 34) φ.115 inch R6 (FIG.34) φ.100 inch R7 (FIG. 34)    φ.115 inch-φ.130 inch R8 (FIG. 34) φ.110inch R9 (FIG. 34)    φ.100 inch-φ.130 inch

For example, the screw 12 may have a length D11 (FIG. 3) ranging from 10mm-60 mm, and the receiver 20 may have a diameter D12 (FIG. 8) rangingbetween 2 mm-10 mm. The compression member 40 may define the channel 42having the width D8 ranging between 2 mm-12 mm. The channels 32 and 34may comprise dimensions D5, D6 (FIGS. 3 and 17) ranging between 2 mm-10mm. It should be understood, however, the other shapes and dimensionsmay be used without departing from the true spirit and scope of theinvention.

Advantageously, this system and method provide a capless multiaxialscrew which eliminates the need for caps or screws or threads of thetype used in the prior art. This system and method combine a verysimplified yet effective means for locking an elongated member or rod 24to a screw 12 and spinal bone in the manner described and shown herein.

While the apparatus, system and method herein described, and the form ofapparatus for carrying this method into effect, constitute severalillustrative embodiments of this invention, it is to be understood thatthe invention is not limited to this precise method and form ofapparatus, and that changes may be made in either without departing fromthe scope of the inventions, which is defined in the appended claims.

1. A capless multiaxial screw fixation assembly comprising: a screwhaving a threaded portion and a screw head; a receiver having a bore forreceiving said threaded portion and a receiving channel for receiving anelongated member, said receiving channel further comprising a lockingchannel in communication with said receiving channel; a compressionmember for situating in said bore, said compression member comprising: asecond receiving channel having a first end and a second end and furtherassociated with a first end; and a seat area associated with said secondend for receiving and engaging said screw head; said elongated membercooperating with said compression member to lock said elongated memberto said screw when said elongated member is received in said first andsecond receiving channels and said receiver is rotated from an unlockedposition to a locked position.
 2. The capless multiaxial screw fixationassembly as recited in claim 1 wherein said receiver comprises aplurality of channels that capture said elongated member.
 3. The caplessmultiaxial screw fixation assembly as recited in claim 2 wherein each ofsaid plurality of channels defines an intermediate area for capturingsaid elongated member to facilitate adjusting a position of saidelongated member before it is locked in said receiver.
 4. The caplessmultiaxial screw fixation assembly as recited in claim 3 wherein saidplurality of channels are defined by a first surface and a secondsurface, each of said plurality of channels having an intermediate stepfor defining said intermediate area.
 5. The capless multiaxial screwfixation assembly as recited in claim 1 wherein said screw, receiver andcompression member are preassembled.
 6. The capless multiaxial screwfixation assembly as recited in claim 1 wherein said locking channel isa helical channel defined by at least one surface of said receiver. 7.The capless multiaxial screw fixation assembly as recited in claim 1wherein said seat area is generally concave, said screw head having acurvature that generally complements said concave receiving area.
 8. Thecapless multiaxial screw fixation assembly as recited in claim 1 whereinsaid receiving channel comprises a first axis and said second receivingchannel comprises a second axis, said second axis and said first axisbeing generally parallel when said receiver is in said unlocked positionand generally perpendicular when said receiver is actuated to saidlocked position.
 9. The capless multiaxial screw fixation assembly asrecited in claim 1 wherein when said receiver is rotated, said receivermoves from a first position to a second position in response thereto,such that when said receiver is in said second position, said elongatedmember is closer to said screw head than when said elongated member isin said first position.
 10. The capless multiaxial screw fixationassembly as recited in claim 9 wherein said first position correspondsto said unlocked position and said second position corresponds to saidlocked position.
 11. The capless multiaxial screw fixation assembly asrecited in claim 1 wherein said receiving channel is generallyperpendicular to an elongated member axis of said elongated member whensaid receiver is in said locked position.
 12. The capless multiaxialscrew fixation assembly as recited in claim 1 wherein said lockingchannel provides a bayonet connection between said elongated member andsaid screw.
 13. The capless multiaxial screw fixation assembly asrecited in claim 1 wherein said receiving channel is generally parallelalong an axis of said receiver and said locking channel spirals aboutthe axis of said receiver when moving in an axial direction.
 14. Thecapless multiaxial screw fixation assembly as recited in claim 1 whereinsaid receiving channel extends from an end of said receiver in adirection that is generally parallel to an axis of said receiver andsaid locking channel extends in a direction that is generally notparallel to said axis of said receiver.
 15. The capless multiaxial screwfixation assembly as recited in claim 1 wherein when said compressionmember is received in said bore and said first channel becomes generallyaligned with said second channel, said locking channel becomes situatedat least partially around said compression member.
 16. The caplessmultiaxial screw fixation assembly as recited in claim 1 wherein saidreceiver comprises at least one camming surface that cooperates with anopposing surface for defining said locking channel, said at least onecamming surface facilitates camming said elongated member urges saidcompression member to apply a compressive force against said compressionmember which, in turn, urges said compression member to apply acompressive force against said screw head in response thereto.
 17. Thecapless multiaxial screw fixation assembly as recited in claim 1 whereinsaid receiver comprises a plurality of camming surfaces that cooperatewith a plurality of opposing surfaces, respectively, to define saidlocking channel, said plurality of camming surfaces camming against saidelongated member to force said elongated member against said compressionmember which, in turn, applies a compressive force against said screwhead when said receiver is rotated.
 18. The capless multiaxial screwfixation assembly as recited in claim 17 wherein said locking channelcomprises a first locking channel area and a second locking channelarea, said receiver comprises a first camming surface generally opposedto a first opposing surface to define said first locking channel areaand a second camming surface generally opposed to a second opposingsurface to define said second locking channel area, said first andsecond camming surfaces camming against said elongated member to forcesaid elongated member against said compression member which, in turn,applies a compressive force against said screw head when said receiveris rotated.
 19. The capless multiaxial screw fixation assembly asrecited in claim 1 wherein said locking channel comprises a lock memberassociated therewith for facilitating retaining said receiver in alocked position.
 20. The capless multiaxial screw fixation assembly asrecited in claim 19 wherein said lock member comprises a detent in saidreceiver and associated with said locking channel.
 21. The caplessmultiaxial screw fixation assembly as recited in claim 20 wherein saidlock member cooperates with an end wall of said locking channel todefine a locking area at which said elongated member is locked when itis in said locked position.
 22. The capless multiaxial screw fixationassembly as recited in claim 1 wherein said receiving channel lies in afirst plane that is generally planar and said locking channel lies in asecond plane that is non-planar.
 23. The capless multiaxial screwfixation assembly as recited in claim 22 wherein said second planespirals about an axis of said retainer.
 24. The capless multiaxial screwfixation assembly as recited in claim 1 wherein said locking channelspirals about an axis of said retainer.
 25. The capless multiaxial screwfixation assembly as recited in claim 1 wherein said screw head isgenerally spherical and said seat area is also generally spherical anddimensioned to receive and complement said screw head.
 26. A spinalfixation assembly comprising: a receiver having a bore for receiving ascrew having a screw head that is larger received in said bore; and acompression member dimensioned to be received in said bore and having afirst end for receiving an elongated member and a second end forengaging said screw head; said receiver comprising a receiving channelfor receiving said elongated member and a locking channel for lockingsaid elongated member to said screw when said receiver is rotated froman unlocked to a locked position.
 27. The spiral fixation assembly asrecited in claim 26 wherein said locking channel spirals about an axisof said receiver.
 28. The spiral fixation assembly as recited in claim26 wherein said locking channel and said receiving channel cooperate toprovide a bayonet connection between said elongated member and saidscrew.
 29. The spiral fixation assembly as recited in claim 26 whereinsaid bore comprises a generally rounded or tapered seat associated witha coupling end of said receiver, said screw head comprising a roundedprofile and received in said rounded seat to permit said receiver tomove polyaxially relative to said screw after said screw is mounted intoa vertebra.
 30. The spiral fixation assembly as recited in claim 26wherein said bore comprises a diameter that is greater than across-sectional dimension of said receiving channel and said compressionmember comprises a diameter that is received in said bore.
 31. Thespiral fixation assembly as recited in claim 26 wherein said borecomprises a bore diameter that is greater than a cross-sectionaldimension of said receiving channel and said compression membercomprising a compression member diameter that is greater than saidcross-sectional dimension of said receiving channel, but less than saidbore diameter.
 32. The spinal fixation assembly as recited in claim 26wherein said compression member comprises a second receiving channel,wherein said receiving channel comprises a first axis and said secondreceiving channel comprises a second axis, said second axis and saidfirst axis being generally parallel when said elongated member is insaid unlocked position and generally perpendicular when said elongatedmember is in said locked position.
 33. The spinal fixation assembly asrecited in claim 26 wherein when said receiver is rotated from saidunlocked position to said locked position, said elongated member becomessecured to said screw and situated closer to said screw.
 34. The spinalfixation assembly as recited in claim 33 wherein when said receiver isin an unlocked position, said receiving channel becomes generallyaligned with a second receiving channel in said compression member. 35.The spinal fixation assembly as recited in claim 26 wherein saidreceiving channel is generally perpendicular to an elongated member axisof said elongated member when said receiving member is in said lockedposition.
 36. The spinal fixation assembly as recited in claim 26wherein said locking channel spirals from a first end of said receivertoward a second end of said receiver.
 37. The spinal fixation assemblyas recited in claim 26 wherein said locking channel defines a helix. 38.The spinal fixation assembly as recited in claim 26 wherein saidreceiving channel extends from an end of said receiver in a directionthat is generally parallel to an axis of said receiver and said lockingchannel extends at least partially about said axis of said receiver. 39.The spinal fixation assembly as recited in claim 26 wherein saidcompression member comprises a second receiving channel that becomesgenerally aligned with said receiving channel when said elongated memberis received in said receiver and said first and second receivingchannels becoming generally perpendicular when said receiver is rotatedto said locked position.
 40. The spinal fixation assembly as recited inclaim 26 wherein said receiver comprises at least one camming surfacethat cooperates with an opposing surface for defining said lockingchannel, said at least one camming surface camming against saidelongated member to move said elongated member against said compressionmember which, in turn, applies a compressive force against said screwhead in response thereto.
 41. The spinal fixation assembly as recited inclaim 26 wherein said receiver comprises a plurality of camming surfacesthat cooperate with a plurality of opposing surfaces, respectively, todefine said locking channel, said plurality of camming surface cammingagainst said elongated member to force said elongated member againstsaid compression member which, in turn, applies a compressive forceagainst said screw head when said receiver is rotated.
 42. The spinalfixation assembly as recited in claim 26 wherein said locking channelcomprises a first locking channel area and a second locking channel;said receiver comprises a first camming surface generally opposed to afirst opposing surface to define said first locking channel area and asecond camming surface generally opposed to a second opposing surface todefine said second locking channel area, said first and second cammingsurfaces camming against said elongated member to force said elongatedmember against said compression member which, in turn, applies acompressive force against said screw head when said receiver is rotated.43. The spinal fixation assembly as recited in claim 42 wherein saidlocking channel comprises a lock member associated therewith forfacilitating retaining said receiver in a locked position.
 44. Thespinal fixation assembly as recited in claim 43 wherein said lock membercomprises a detent or protrusion or a plurality of detents orprotrusions in said receiver and associated with said locking channel.45. The spinal fixation assembly as recited in claim 43 wherein saidlock member cooperates with an end wall of said locking channel todefine a locking area at which said elongated member is locked when itis in said locked position.
 46. The spinal fixation assembly as recitedin claim 46 wherein said receiving channel lies in a first plane that isgenerally planar and said locking channel lies in a second plane that isnon-planar.
 47. The spinal fixation assembly as recited in claim 26wherein said second plane spirals about an axis of said receiver. 48.The spinal fixation assembly as recited in claim 26 wherein said lockingchannel extends in a direction that is non-axial relative to an axis ofsaid receiver.
 49. The spinal fixation assembly as recited in claim 26wherein said screw head is generally spherical and said compressionmember comprises a seat that is also generally spherical and dimensionedto receive said screw head.
 50. A spinal fixation assembly comprising: areceiver having a bore for receiving a screw having a screw head and areceiving channel in communication with said bore for receiving anelongated member; and a compression member dimensioned to be received insaid bore and having a first end for engaging said elongated member anda second end for engaging said screw head; said receiver comprising arotary lock for locking said elongated member to said screw.
 51. Thespinal fixation assembly as recited in claim 50 wherein said rotary lockcomprises at least one engaging surface for engaging said elongatedmember and for locking said elongated member to said screw when saidreceiver is rotated to a locked position.
 52. The spinal fixationassembly as recited in claim 50 wherein said receiver is generallycylindrical and said bore extends along an axis of said receiver, saidreceiver comprising a first locking aperture in communication with saidbore and a second locking aperture in communication with said bore; saidfirst and second locking apertures cooperating to define said rotarylock.
 53. The spinal fixation assembly as recited in claim 51 whereinsaid first locking aperture and said second locking aperture cooperateto define a locking channel for receiving said elongated member.
 54. Thespinal fixation assembly as recited in claim 51 wherein said firstlocking aperture and said second locking aperture cooperate to define agenerally s-shaped channel when viewed in cross-section for receivingsaid elongated member.
 55. The spinal fixation assembly as recited inclaim 50 wherein said rotary lock comprises a locking channel in saidreceiver that is in communication with said receiving channel.
 56. Thespinal fixation assembly as recited in claim 52 wherein said lockingchannel is defined by a first channel in a wall of said receiver and asecond channel in said wall of said receiver, said first and secondchannels being generally opposed.
 57. The spinal fixation assembly asrecited in claim 56 wherein said first channel and said second channelextend away from the receiving channel about a receiver axis of saidreceiver such that rotation of the receiver will move from an unlockedposition to a locked position.
 58. The spinal fixation assembly asrecited in claim 56 wherein said first channel and said second channelspiral in a common direction about a receiver axis of said receiver. 59.The spinal fixation assembly as recited in claim 55 wherein said lockingchannel and said receiving channel cooperate to provide a bayonetconnection between said elongated member and said screw.
 60. The spinalfixation assembly as recited in claim 55 wherein said receiving channellies in a plane that is generally planar and said locking channel liesin a plane that is generally curved.
 61. The spinal fixation assembly asrecited in claim 55 wherein said receiver comprises a wall that lies inan arcuate plane about a receiver axis of said receiver and said lockingchannel also lie in said arcuate plane.
 62. The spinal fixation assemblyas recited in claim 55 wherein a starting area of said locking channelis situated at a different radial position and a different axialposition relative to said receiver axis when compared to an end positionof said locking channel when said elongated member is locked to saidscrew.
 63. A spinal fixation assembly comprising: a receiver having abore for receiving a screw having a screw head; and a compression memberdimensioned to be received in said bore and having a first end forengagement with an elongated member and a second end for engagement withsaid screw head; said receiver comprising a locking channel and areceiving channel coupling said locking channel; said receiving channelreceiving said elongated member and said locking channels cooperating tosecure said elongated member to said screw when said receiver isrotated.
 64. The spinal fixation system as recited in claim 63 whereinsaid receiver comprises a first engaging surface; said first engagingsurface engaging said elongated member and forcing it against saidcompression member which, in turn, engages said screw head with acompressive force when said receiver is rotated.
 65. The spinal fixationsystem as recited in claim 64 wherein said locking channels comprise afirst camming surface and a second camming surface, respectively, thatengages said elongated member and forces it against said compressionmember until said elongated member becomes fixed relative to said screw.66. The spinal fixation system as recited in claim 63 wherein saidlocking channel lies in a plane that is at predetermined angle relativeto said receiving channel.
 67. The spinal fixation system as recited inclaim 66 wherein said predetermined angle is approximately 90 degrees.68. The spinal fixation system as recited in claim 66 wherein saidpredetermined angle is an acute angle that extends toward a vertebraewhen the screw is screwed into the vertebrae.
 69. A receiver for usewith a polyaxial screw comprising: a body having a bore; and aconnection channel for receiving an elongated member and for locking itto the screw when said receiver is rotated.
 70. The receiver as recitedin claim 69 wherein said connection channel defines a bayonet connectionchannel.
 71. The receiver as recited in claim 70 wherein said connectionchannel comprises a plurality of channels that cooperate to define saidbayonet connection channel.
 72. The receiver as recited in claim 71wherein said plurality of channels spiral about an axis of saidreceiver.
 73. A spinal fixation assembly comprising: a receiver having abore for receiving a screw having a screw head; and a compression memberdimensioned to be received in said bore and having a first end and asecond end; said receiver comprising an integral rotary lock for lockingan elongated member to said screw when said receiver is rotated.
 74. Thespinal fixation system as recited in claim 73 wherein said integralrotary lock comprises a continuous channel for receiving said elongatedmember and for urging said elongated member toward said screw head whensaid receiver is rotated.
 75. The spinal fixation system as recited inclaim 73 wherein said integral rotary lock comprises a first channelthat extends about a receiver axis in a first direction and a secondchannel that extends about said receiver axis in a second direction anda receiver channel coupling said first and second channels.
 76. Thespinal fixation system as recited in claim 75 wherein said first andsecond directions extend away from the receiving channel about areceiver axis of said receiver such that rotation of the receiver willmove from an unlocked position to a locked position.
 77. The spinalfixation system as recited in claim 75 wherein said receiver channellies in a plane that generally extends along an axis of said receiver.78. The spinal fixation system as recited in claim 75 wherein said firstand second channels spiral about said receiver axis.
 79. The spinalfixation system as recited in claim 75 wherein said first and secondchannels lie in imaginary planes that intersect an axis of said receiverat acute angles.
 80. The spinal fixation system as recited in claim 75wherein said receiver channel lies in a receiver plane, said firstchannel lies in a first plane and said second channel lies in a secondplane, first and second planes intersecting said receiver plane at anacute angle that extends toward a vertebrae when the screw is screwedinto the vertebra.
 81. A method for securing an elongated member to aspinal column, comprising the steps of: screwing a screw into a spinalbone, said screw having a head that is received in a seat of a receiverhaving a bore through which threads of the screw may pass; situating theelongated member into said receiver; and rotating the receiver to fastensaid elongated member onto said screw.
 82. The method as recited inclaim 81 wherein said method further comprises the step of: situatingsaid elongated member against a compression member which engages saidscrew head to fasten said elongated member to said screw when saidreceiver is rotated.
 83. The method as recited in claim 82 wherein saidmethod comprises the step of: aligning a receiving channel of saidcompression member with a receiving channel of said receiver before saidsituating step.
 84. The method as recited in claim 82 wherein saidmethod comprises the step of providing the compression member andreceiver pre-aligned prior to said screwing step.
 85. The method asrecited in claim 81 wherein said retainer comprises a receiving channeland a locking channel, said method further comprising the steps of:situating said elongated member in said receiving channel; rotating saidreceiver so that said elongated member becomes situated in said lockingchannel.
 86. The method as recited in claim 85 wherein said methodfurther comprises the step of: aligning said receiver before saidrotating step.
 87. The method as recited in claim 85 wherein said methodfurther comprises the steps of: screwing a second screw into a secondspinal bone, said second screw having a head that is received in a seatof a second receiver having a bore through which threads of the secondscrew may pass; situating said elongated member into said secondreceiver; and rotating the second receiver to fasten said elongatedmember onto said second screw after performing said first rotating step,thereby fixing the relative positions of said first and second spinalbones.
 88. The method as recited in claim 87 wherein said method furthercomprises the step of: aligning a first receiving channel of said firstreceiver with a second receiving channel of said second receiver beforesaid second rotating step.
 89. The method as recited in claim 81 whereinsaid method further comprises the step of: repeating said method using aplurality of screws having a plurality of retainers, respectively, andsaid elongated member to secure a plurality of vertebrae together in afixed relationship.
 90. A capless multiaxial screw comprising: a screwhaving a threaded portion and a screw head; and a receiver having a borefor receiving said threaded portion and a receiving channel forreceiving an elongated member, said receiving channel further comprisinga locking channel in communication with said receiving channel; saidreceiver locking said elongated member to said screw when said elongatedmember is received in said receiving channel and said receiver isrotated from an unlocked position to a locked position.
 91. The caplessmultiaxial screw as recited in claim 90 wherein said receiver comprisesa plurality of channels that capture said elongated member.
 92. Thecapless multiaxial screw as recited in claim 91 wherein each of saidplurality of channels defines an intermediate area for capturing saidelongated member to facilitate adjusting a position of said elongatedmember before it is locked in said receiver.
 93. The capless multiaxialscrew as recited in claim 92 wherein said plurality of channels aredefined by a first surface and a second surface, each of said pluralityof channels having an intermediate step for defining said intermediatearea.
 94. The capless multiaxial screw as recited in claim 93 wherein atleast one of said first and second surfaces is not planar.
 95. Thecapless multiaxial screw as recited in claim 90 wherein said lockingchannel is a helical channel defined by at least one surface of saidreceiver.
 96. The capless multiaxial screw as recited in claim 90wherein said capless multiaxial screw further comprises a compressionmember for situating in said bore, said compression member comprising agenerally concave seat, said screw head having a curvature thatgenerally complements said generally concave seat.
 97. The caplessmultiaxial screw as recited in claim 90 wherein said receiving channelcomprises a first axis, said elongated member axis of said elongatedmember being generally parallel to said first axis when said elongatedmember is in said unlocked position and generally perpendicular whensaid receiver is actuated to said locked position.
 98. The caplessmultiaxial screw as recited in claim 90 wherein when said receiver isrotated, said receiver moves said elongated member from a first positionto a second position in response thereto, such that when said receiveris in said second position, said elongated member is locked to saidscrew head.
 99. The capless multiaxial screw as recited in claim 90wherein when said receiver is rotated, said receiver moves saidelongated member from a first position, through an intermediateposition, to a second position.
 100. The capless multiaxial screw asrecited in claim 98 wherein said first position corresponds to saidunlocked position and said second position corresponds to said lockedposition.
 101. The capless multiaxial screw as recited in claim 90wherein said receiving channel is generally perpendicular to anelongated member axis of said elongated member when said receiver is insaid locked position.
 102. The capless multiaxial screw as recited inclaim 90 wherein said locking channel provides a bayonet connection.103. The capless multiaxial screw as recited in claim 90 wherein saidreceiving channel is generally parallel along an axis of said receiverand said locking channel spirals about said axis of said receiver whenmoving in an axial direction.
 104. The capless multiaxial screw asrecited in claim 90 wherein said receiving channel extends from an endof said receiver in a direction that is generally parallel to an axis ofsaid receiver and said locking channel extends in a direction that isgenerally not parallel to said axis of said receiver.
 105. The caplessmultiaxial screw as recited in claim 90 wherein said receiver comprisesat least one camming surface that cooperates with an opposing surfacefor defining said locking channel, said at least one camming surfacefacilitates compressing said elongated member against said screw. 106.The capless multiaxial screw as recited in claim 90 wherein saidreceiver comprises a plurality of camming surfaces that cooperate with aplurality of opposing surfaces, respectively, to define said lockingchannel, said a plurality of camming surfaces for camming against saidelongated member to lock said receiver to said screw.
 107. The caplessmultiaxial screw as recited in claim 106 wherein said locking channelcomprises a first locking channel area and a second locking channelarea, said receiver comprises a first camming surface generally opposedto a first opposing surface to define said first locking channel areaand a second camming surface generally opposed to a second opposingsurface to define said second locking channel area, said first andsecond camming surfaces camming against said elongated member to forcesaid elongated member against said compression member which, in turn,applies a compressive force against said screw head when said receiveris rotated.
 108. The capless multiaxial screw as recited in claim 90wherein said locking channel comprises a lock member associatedtherewith for facilitating retaining said receiver in a locked position.109. The capless multiaxial screw as recited in claim 108 wherein saidlock member comprises a detent in said receiver and associated with saidlocking channel.
 110. The capless multiaxial screw as recited in claim109 wherein said lock member cooperates with an end wall of said lockingchannel to define a locking area at which said receiving member islocked when it is in said locked position.
 111. The capless multiaxialscrew as recited in claim 90 wherein said receiving channel lies in afirst plane that is generally planar and said locking channel lies in asecond plane that is non-planar.
 112. The capless multiaxial screw asrecited in claim 111 wherein said second plane spirals about an axis ofsaid retainer.
 113. The capless multiaxial screw as recited in claim 90wherein said locking channel spirals about an axis of said retainer.114. The capless multiaxial screw as recited in claim 90 wherein saidreceiver comprises a seat, said screw head is being generally sphericaland said seat is also generally spherical and dimensioned to receive andcomplement said screw head.